1. Field of the Invention
The present invention relates to an ignition plug cap for connecting an ignition plug with a high tension cable in an automotive engine in which an ignition plug is accommodated in an ignition plug mounting hole formed in the engine block thereof, wherein the ignition plug cap is composed of three principal members; a rain cover, a plug cap pipe and a rubber cap.
2. Description of the Prior Art
Heretofore, there have been provided various ignition plug caps for connecting an ignition plug with a high tension cable in an automotive engine in which an ignition plug is accommodated in an ignition plug mounting hole formed in the engine block thereof, a case in point being the one disclosed in FIG. 2.
In the figure, it is shown that the ignition plug cap is composed of a three principal members; a plug cap pipe 1 which is provided with an empty hole 4 for accommodating a plug terminal of the ignition plug and covering also a high tension cable 6 and a connection terminal 2, a rain cover 5 made of a resilient material and covering the upper end portion of the plug cap pipe 1 and a rubber cap 3 which is also made of a resilient material such as silicon rubber attached to the lower end portion of the plug cap pipe 1.
Here, the rain cover 5 is fitted with the upper end portion of the ignition plug mounting hole formed in an engine block for prohibiting immersion of waterdrops or the like into the mounting hole and also for properly positioning and holding the plug cap itself. The connecting terminal 2 electrically connects a plug terminal of the ignition plug (not shown) inserted to the empty hole 4 with the high tension cable 6. The plug cap pipe 1 prevents a high voltage applied to the connecting terminal 2 and the plug terminal of the ignition plug from leaking into the engine block. Further, the rubber cap 3 is fitted with an insulator of the ignition plug for properly positioning and holding the ignition plug itself, and prohibiting simultaneously the moisture substance from immersing into the plug terminal of the ignition plug and to the connecting terminal 2, to which a high electric voltage is applied, so as to prevent the leaking thereof into the engine block and provide thereby a secure ignition of the ignition plug. It is to be noted that as a rubber cap anti-defection mechanism, the plug cap pipe 1 is provided with an annular projection rib 1a and the rubber cap 3 is provided with an annular groove 3a for receiving the annular projection rib 1a.
In the above construction, however, there has been such a problem that the rubber cap 3 and the plug cap pipe 1 are made of different materials respectively, and thus not made as an integral body. For this reason, when removing the ignition plug cap from the ignition plug mounting hole for its maintenance and/or replacement purpose, the rubber cap 3 is abutted against the side surface of this mounting hole, as shown in FIG. 3, resulting that the upper end portion of the rubber cap 3 is ripped off.
In this case, if, after a detection and/or a replacement of the ignition plug, the ignition plug cap is reinserted into the ignition plug mounting hole with the rubber cap 3 being left in the ripped off state, and supposing that an immersion of waterdrops to the mounting hole occurs and the moisture is attached to the plug cap pipe 1, then the connected portion between the ignition plug and the connecting terminal 2, to which a high voltage is applied, also gets wet, generating thereby an imperfect insulation therebetween. By the way, the voltage normally applied to ignition plugs is between 15 Kv and 20 Kv, so that even such extremely subtle moisture could leak into the engine block, impeding thereby a normal starting-up operation of the engine.
Further, it is to be noted that the ignition plug cap as above is made by applying an insert molding operation to the rubber plug cap 3 after the fabrication of the plug cap pipe 1. However, as it is not possibly control to put the plug cap pipe 1 in a mould at a perfectly proper position, a molding operation with the plug cap pipe being left upright with respect to the mould split surface cannot be conducted, due to which the plug cap pipe has to be laid during the molding operation. Therefore, the number of outputs obtained by one molding procedure becomes small, resulting that the manufacturing cost of the ignition plug becomes high.
The present invention is made for solving the above problem, and it is an object of the present invention to provide an ignition plug cap in which the rubber cap is not readily ripped off even during a detecting and/or repairing operation, providing thereby a comfortable working condition, a stable engine starting operation, and also providing an efficient productivity thereof.